Hello mdyune,
Thank you for joining us today. As to your question, being a US citizen you are taxed on your global income, so you should be paying capital gains on crypto trading in a different country. Whether or not you have to pay tax in that foreign country will depend on that country's laws.
If you do end up having to pay taxes to that other country, you can claim a foreign tax credit on your US tax return for the taxes paid to that other country. The taxes will be calculated differently and there are limits involved in how much you can take each year, but rest assured that you shouldn't be paying double taxes on the same income.
I hope that helps.