How has immigration changed the politics of united states and does illegal immigration pose a serious threat to the economy?

Immigration has become one of the most divisive issue between the two dominant political party in united states (republican tend to favor controlled immigration while the Democrats tend to make immigration more lenient).

Personally, I believe immigration does possess a certain level of threats to the economy BUT ONLY if the immigrants that came in do not possess a necessary skill that could contribute to US economy.

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