Yes, you can use your old visa. You need to bring both passports AND evidence of name change, such as marriage certificate. Additionally if your evidence is not in English (i.e. Paraguay marriage certificate in Spanish), you need to bring a certified English translation.
See for example https://th.usembassy.gov/visas/nonimmigrant-visas/non-immigrant-visas-frequently-asked-questions (look at If I already have a valid visa and I change my name (through marriage, or for other reasons), can I use my old visa? question):
Yes. As long as your passport is still valid for at least six months
beyond the date you plan on traveling, you may use your existing visa.
However, you should carry proof of your legal name change (i.e., the
Thai name change certificate with a certified English translation)
with you when you travel to the U.S. If you wish to reduce the
likelihood of encountering a delay at the port of entry, you are
welcome to apply for a new visa by following our normal application
procedures.
This of course is only relevant if your last name changes. If you keep your old last name, you can still use your visa and passport. Your marital status is not recorded on the US visa.
