Am I of legal age abroad too?

I moved to the United States to study for a few months. I've just turned 18 and I know that in this country, the age of majority is 21. I'm wondering whether, as a Swiss national, I can claim the age of majority applicable in my country of origin?
K.

As you know, in Switzerland, the age of majority is set at 18, in accordance with Article 14 of our Civil Code. On reaching this age, a young man or woman becomes fully capable of exercising his or her civil rights, unless restricted by protective measures.
To find out what happens to these privileges when a Swiss national travels abroad, it is necessary to examine the principles of private international law and the legal particularities of the countries concerned.
Civil majority is a question of personal status, and each country has sovereignty over the age at which a person is considered to have legal capacity on its territory. For example, an 18-year-old Swiss is legally of age under Swiss law, which means that he or she can enter into contracts, marry without parental consent or vote (insofar as these rights are recognised for adults), but this status may be called into question when he or she travels or resides abroad.
It is private international law that governs situations where several national jurisdictions are involved. In Switzerland, the Federal Act on Private International Law (LDIP) provides that the enjoyment of civil rights is governed by Swiss law, including the age of majority.
For example, a Swiss citizen is still considered to be of age 18 in Switzerland, even if he or she is in a country where the age of majority is higher. However, many countries apply the principle of territoriality, according to which local law takes precedence over the personal status of foreigners when it comes to acts performed on their soil.
In a country where you have to wait until the age of 21 to enjoy all your rights, an 18-year-old Swiss could be refused certain local legal acts such as signing a contract, entering certain establishments or consuming alcohol. This situation is common in countries such as the United States, where the legal drinking age is 21, even though the majority age is 18.