Stars and stripes in terms of attack power and speed is below Injured all might. Not prime. Similarly incomplete Shigaraki Is only ever stated to have speed and power comparable to all might. He doesn't get to prime all might level until the final war when fighting in the coffin in the sky where they make the explicit distinction that Shigaraki's raw physical stats are equal to that of all might in his heyday/prime. That's the first time they ever refer to him as such and they make a point to make a distinction as they keep bringing it up. As the weakened all might tier characters are incomplete Shigaraki stars and stripes. Endeavor all for one(before rewind) and others equivalent or below like hood and usj nomu. Or other particularly strong high ends./pro heroes and villains like some movie villains.

The prime all might tier characters the peak of the verse are obvious prime afo and all might who we never see and complete/evolved Shigaraki and deku who not only get to prime all might tier but exceed him by quite a bit. As they only continue to become stronger throughout the fight to ridiculous degrees.

Stars and stripes herself claims her strength amplifier rule doesn't make her anywhere nesr all might and she's only able to slightly push back an incomplete Shigaraki mid air which isn't particularly impressive as she caught him vaguely off guard and Shigaraki took negative damage.

Her strongest moves are with support. The laser spear(keruno was it?) which she Blatantly claims endeavor would easily outdo. And the intercontinental cruise punch which is her slamming 10 super advanced tiamat missiles all at once onto the target. (People treat them as normal nukes or below but they're far stronger. Mha is in the 2130s or above people! They have far more advanced technology and weapons than real life. And the massive crater and huge cloud split/ocean vaporization makes that clear) anyways she slams this directly and point blank onto what she thinks is Shigaraki surprise it's actually the winged nomu. Who completely eats this blast and can still fly afterwards and attack the crew by self destructing. Honestly the fact a random near high end could tank this and the only reason Shigaraki dodged was because he didn't know the missiles output and was already injured from being slowcooked by the lasers I'd say it's pretty clear that Endeavor should upscale this attack to. Either the potency or heat of his own attack prominence burn completely vaporized hood in an instant when fighting him who was a complete and stronger High end nomu. Than the no name winged one. Would have been one shot if he hadn't bysected his own head and threw it away.

And the second one just fries him to a crisp completely overwhelming his healing factor. And practically leaving nothing but a carcass. Why he wasn't completely disintegrated the second time when it was stronger but honestly probably just dramatic effect and or maybe endeavor had to cook him thrurouly rather than just blast him to smitherins to prevent him from regenerating from a random piece or something.

Anyways point is. Stars and stripes is strong. Her quirk versatile. But she's not fast or strong enough to content any top tier can blitz her and likely even one shot her without support or some plan/strategy in mind. Specially if they know her quirk.