If you can handle spending a holiday in Berwyn, Independence Day at FitzGerald’s provides an opportunity to see two bands that make me prouder to be an American than a lifetime supply of rockets and red glare. Nobody has done more to save the accordion from Lawrence Welk’s Disease than Clifton Chenier, whose Bogalusa Boogie album will probably stand indefinitely as zydeco’s finest hour on vinyl. Accompanied by his brother Cleveland, on rub board, and the accurately named Red Hot Louisiana Band, Chenier plays a festive hybrid of Cajun swamp music, French-Acadian waltzes, Delta blues, and jazz. Often in poor health, Clifton sometimes needs an extra push to turn his shows from great fun into great art. That push may come from Chicago’s own Lil’ Ed & the Blues Imperials. The diminutive Ed Williams, whose giant slide-guitar sound derives from the likes of Elmore James and his own uncle, J.B. Hutto, spent a tough decade shaking his moneymaker for small change in the west-side clubs until last year, when he stepped into his first recording studio and played a set so hot that Alligator Records decided to cut the Roughhousin’ album on the spot. (Ed plays on Saturday only.) Tonight and Saturday, FitzGerald’s, 6615 Roosevelt, Berwyn; 788-2118.