FISA was established during the Carter administration in 1978, long before the Patriot Act.
You are absolutely correct. The Patriot Act put FISA on steroids and focused it on American citizens.
From the Brennan Center for Justice:
The government claims that the telephone records program that was the subject of the leaked Verizon court order is authorized under the so-called “business records” provision of the Foreign Intelligence Surveillance Act (FISA), first enacted in 1978. That provision was amended by Section 215* of the Patriot Act in 2001. Section 215 allows the government to obtain a secret court order requiring third parties, such as telephone companies, to hand over any records or other “tangible thing” if deemed “relevant” to an international terrorism, counterespionage, or foreign intelligence investigation. Section 215 orders may have been combined with requests under other provisions of the Patriot Act, such as Section 216, which governs access to online activity, such as email contact information or Internet browsing histories.
With respect to PRISM, the government cites Section 702 of the FISA Amendments Act, a law first passed in 2008 and reauthorized in 2012. Section 702 allows the government to acquire foreign intelligence by targeting non-U.S. persons “reasonably believed” to be outside U.S. borders. The law explicitly prohibits intentionally targeting people known to be located inside the U.S. at the time the government acquires the data. It also requires the government to establish certain “targeting procedures” to ensure that the government is targeting people “reasonably believed” to be outside the United States (which can be difficult to ascertain when dealing with internet or cell phone communications). In addition, the government must adopt “minimization procedures” to guard against the inadvertent collection, retention, and dissemination of information about U.S. persons.