Yes. According to the Flag Code, a flag can be anything which shows the colors, the stars and the stripes, in any number of either thereof, or of any part or parts of either, by which the average person seeing the same without deliberation may believe the same to represent the flag, colors, standard, or ensign of the United States of America.
Source: Flag Code, Section 3
Therefore, a flag includes any representation of it of any substance including T-shirts and ties.
Other references in the Flag Code related to this question are:
- The flag should not be used as wearing apparel, bedding, or drapery. (section 8d)
- It should not be embroidered on such articles as cushions or handkerchiefs and the like (section 8i)
- It should not be printed or otherwise impressed on paper napkins or boxes (section 8i)
- The flag should never have , nor on any part of it, nor attached to it any mark, insignia, letter, word, figure, design, picture, or drawing of any nature. (section 8g)
- No part of the flag should ever be used as a costume or athletic uniform. (section 8j)
The Flag Code states that the flag should never be worn. (Section 8d): “The flag should never be used as wearing apparel.”