Most countries allow dual citizenship. The USA doesn't. Canadians who become US citizens automatically retain Cnanadian citizenship too.
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Whatever you do, do not renounce US citizenship. The US has a law that lets them confiscate most of your assets if you do.
The US does allow dual citizenship. I know a number of people with dual citizenship in the US and some other country, usually Canada.
Years ago the US stripped anyone of US citizenship who became a citizen in another country, but that changed. Someone took citizenship elsewhere and then sued the US State department for revoking his citizenship against his will. Courts upheld his US citizenship. The US State department didn't like it and kept it low profile. I read the resulting document which strongly discouraged a US citizen from becoming a citizen in any other country and warned that doing so risked losing US citizenship. I asked the US counsel in another country about the risk of losing US citizenship, and got this reply, verbally, “I have to warn you that you may lose your US citizenship. Off the record, not a chance.”
If you consider taking citizenship elsewhere, learn all you can about tax laws and unintended consequences. Most countries tax residents, but the US taxes citizenship, no matter where in the world the citizen lives. Most taxes are paid in one country or the other but there are a few things that are double taxed, with both nations claiming certain capital gains, or one country taxing something that is tax free in the other, etc. The problem is that until they hit you with some blind tax, or a new reporting rule, you don't know what you don’t know. Consulting a lawyer and a tax accountant who specialize in dual filings and cross border laws is worth the money.
There are usually some downsides to dual citizenship, as well as some advantages, and each person has to decide if his situation makes the negatives worthwhile.
