Why do you think the united states put a limit on the number of immigrants who may enter the country?

Immigration law is very complex, and there is much confusion as to how it works. The Immigration and Naturalization Act (INA), the body of law governing current immigration policy, provides for an annual worldwide limit of 675,000 permanent immigrants, with certain exceptions for close family members. Lawful permanent residency allows a foreign national to work and live lawfully and permanently in the United States. Lawful permanent residents (LPRs) are eligible to apply for nearly all jobs (i.e., jobs not legitimately restricted to U.S. citizens) and can remain in the country even if they are unemployed. Each year the United States also admits noncitizens on a temporary basis. Annually, Congress and the President determine a separate number for refugee admissions.

Both the han and the roman empire decline as a result of social unrest during their collapse.