The Senate last week overwhelmingly approved a bill aimed at comprehensive immigration reform. But conservative opposition to creating a path to citizenship for immigrants in the country illegally gives the sweeping legislation an uncertain fate in the Republican-controlled House of Representatives.

Eleven million undocumented immigrants live in the United States, but not everyone who leaves their native country for a better life aims to settle in America. Countries across the globe have had to decide who to let inside their borders.

As immigration reform comes to a head, we take a look at how other countries—those that have been recognized for having some of the most open, or the most restrictive, immigration policies—are dealing with their huddled masses.

Canada

To combat a shortage of skilled labor that has been stifling the country's economic growth since the 1970s, Canada has adopted one of the most open immigration policies in the world. As of 2010, the foreign-born population makes up 21.3 percent of the country's total population.

On April 1, the already immigration-friendly country launched a Start-up Visa Program in an effort to attract highly skilled foreign entrepreneurs. Immigrants with funding from Canadian venture capital firms or investment groups for a start-up business will be eligible for immediate permanent residency. If the new business fails, the entrepreneur will not be subject to deportation.

Japan

In a country where nationals favor a racially unique and homogenous society, the foreign population accounted for only 1.7 percent of the total population in 2010, according to the Organisation for Economic Co-operation and Development. Japan's strict immigration—or, rather, anti-immigration—policies have drawn heavy criticism.

Like Canada, Japan is facing a rapidly declining population in which the low birthrate can barely match the death rate of the country's senior citizens. The population now sits at 128 million, but analysts estimate the number will have shrunk by a third in 2060, forcing the country to embrace more open policies.

Following the examples of Canada and the United Kingdom, Japan rolled out a new point-based system last spring to rate immigrants. Immigrants earn points based on their academic background and research or business experience, among other factors. Those who score higher—mainly professionals like professors, doctors, and corporate managers—will be given preferential treatment.

Australia

In 2012, Australia received a total of nearly 15,800 asylum claims, up 37 percent from the previous year, according to the United Nations. The country's Department of Immigration and Citizenship states that the Migration Act 1958 requires any noncitizen or person who is unlawfully in Australia to be detained. People without a valid visa are considered unlawful—including children. Migrant children, especially asylum seekers, have been detained in immigration detention centers for months or even years.

The Australian Government has responded to human rights complaints by removing children from detention centers and into community detention, or local housing. However, as of February 2013, there were still 1,062 children in the detention centers, according to the Australian Human Rights Commission.

Amid all the controversy, reports in April indicated that preparations have been made to bring children back to the notorious Curtin Immigration Detention Centre, which closed down in 2002 due to riots and protests. It reopened in 2011 and currently holds only adult single men. A portion of the center could be declared an "alternate place of detention," which the government does not define as a detention center.

Denmark

Denmark's stance on immigration has often been considered controversial. The largely homogenous country has reportedly offered immigrants cash incentives to leave if they cannot assimilate into Danish culture. The incentive was driven by the far-right Danish People's Party, which states on its website that "Denmark is not an immigrant-country and never has been. Thus we will not accept transformation to a multiethnic society."

One of Denmark's most scrutinized laws on immigration is the 24-year rule, which states that in order for the foreign spouse of a Danish citizen to qualify for citizenship both the Danish spouse and the foreign spouse must be at least 24 years old. The rule's purpose is to limit the number of immigrants, prevent forced marriages, and create a better integration process, according to a report by humanityinaction.org.

However, the law has prevented families from reuniting, sparking a debate over possible human rights violations. There are special circumstances where the law can be waived, such as if the spouse is a refugee, has underage children with connections to Denmark, or is handicapped or seriously ill.

Sweden

Sweden, which ranked first among 33 countries in the Migrant Integration Policy Index (MIPEX), is well-known for welcoming Muslim refugees fleeing war-torn nations like Iraq, Syria, and Somalia. But growing unemployment, which sits at 16 percent among foreign residents, and a recent string of violent riots have politicians and citizens questioning its open-door immigration policy.

Some critics point their fingers at costly liberal policies that created an abundance of jobs and attracted a steady flow of immigrant labor from nearby European countries. When job creation slowed, working immigrants stopped entering the country while the flow of unemployed, government-dependent asylum seekers picked up. In 2012, the number of asylum seekers arriving in Sweden jumped nearly 50 percent from the year before—hitting 43,900, the second highest year on record.

Opposition to immigration may still be in the minority, but the need for a more sustainable immigration policy has shot the Sweden Democrats, the far-right anti-immigration political party, up to third place in the polls and may give them political momentum in the 2014 elections.

United Kingdom

The United Kingdom saw a dramatic spike of immigrants in the last decade—from 4.6 million in 2001 to nearly 7.5 million in 2011, according to the U.K. Census. With the annual number of people entering the country far exceeding the number of those leaving, immigration has become the public's most important issue.

Adding to the problem, the U.K. Border Agency discovered last July that hundreds of thousands of migrants with expired visas may still be residing in the country, prompting the prime minister to call for tougher immigration reforms aimed at visa abusers. In late March, Immigration Minister Mark Harper announced that the government was considering a measure that will slap a £1,000 (U.S. $1,532) fee on migrants coming to the U.K. to work or study. The fee will serve as a security bond to be returned only when immigrants return home following the expiration of their visas.