On the status of onglides in American English

In many languages the issue arises as to whether an onglide patters as part of the syllable onset or forms the first part of a (rising) diphthong with the immediately following vowel. If it is part of the syllable onset, the structure of a CGV syllable would be as in (1), but if it forms the first part of a diphthong the structure of a CGV syllable could either be as in (2a) with a monomoraic diphthong (where the glide is ‘co-moraic’ with the following vowel) or as in (2b) with a bimoraic diphthong (C = consonant, G = glide, V = vowel, μ = mora, and σ = syllable).