IMO Mandarin is pretty difficult since it has both tones and weird vowels/consonants - I feel like in English most people struggling tend to only have significant trouble with articles and the "th" sound.
https://en.wikipedia.org/wiki/General_American#Gliding_vowel...
For example, the 'i' in 'bright' is a dipthong that sort of glides from 'uh - aye' very quickly.
Many languages have very few dipthongs -- e.g. Japanese and Spanish come to mind, and Mandarin has some, but they're mostly different from English. If you go from a language that has 5 pure vowel sounds like Spanish to something like 15-20 in English (depending on the dialect), it's hard to keep track of them all and pronounce them correctly [1], especially since English orthography hinders rather than helps you, whereas dipthongs in Spanish are pronounced exactly as they're rendered (e.g. cauda is like ca-u-da spoken fast).
https://en.wikipedia.org/wiki/Diphthong#Spanish
Your example would be /kau̯.da/, with the a and u merging into a single syllable diphthong.
No matter how you cut it, English's vowel phonology is much more complicated than Spanish or Japanese. One misconception that native English speakers have is they think their language is simple to pronounce, when it really isn't.
...Gough also took aim at Sir Winton Turbull when the rural MP shouted: 'I am a Country member'. Whitlam quickly responded with 'I remember', which earned an applause from both sides of the house.