The six-member delegation led by hawkish senator Lindsey Graham backed Sisi in the fight against the jihadist Islamic State group, but was cautious when asked to respond to growing accusations of human rights violations committed by Egyptian security forces.
Graham said Sisi was "the right man at the right time" to lead Egypt as the Islamic State group had become a "nightmare" for the entire region.
"There is a desire that Daesh be destroyed in Sinai... the president has expressed his desire to destroy Daesh," Graham said using the Arabic acronym for the IS, which is spearheading an insurgency in the restive peninsula.
When asked about the human rights situation in Egypt, Graham offered a response in stark contrast to the present US administration, which has regularly criticised reported human rights abuses in Egypt.
"I understand that the country is a new democracy and coming out of chaos," told reporters in Cairo.
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"He (Sisi) has to balance security with the rule of law... there are elements that come to Egypt to disrupt the nation and there are many people coming here to help you. Don't treat them all in the same way," the senator added.
Rights groups have accused Egypt's security services of carrying out illegal detentions, forced disappearances of activists and torture of detainees since the ouster of Islamist president Mohamed Morsi in July 2013.
After his removal, a police crackdown targeting Morsi's supporters has left hundreds dead and tens of thousands jailed. Hundreds more have been sentenced to death including Morsi himself.
In March, US Secretary of State John Kerry said there was a "deterioration in the human rights situation in Egypt in recent weeks and months".
Ties between Washington and Cairo deteriorated after Morsi's ouster.
The US froze its annual $1.3 billion of military aid to Egypt, which led Cairo to warm up to Russia and France to meet its arms requirements.
But the aid was later released even as Washington remains critical of the government's rights record.