The question would rather be "Can you NOT be muscular at 5'9 200lbs?". THIS would be difficult. In general the heavier you are the easier it is for you to have powerful muscles, even if not all of your extra weight is made of muscles.
5'9" is 1.75m, so your maximal lean mass could be around 76 kg (but this would be for a high-level strength athlete).
Since 200 lbs is 91 kg, it means you have at least 15 kg of fat, i.e. 16% body fat.
In that case, if you were 200 lbs with 16% BF, you would still look quite athletic.
But of course the average sedentary male is more likely to have a FFMI around 19 kg/m2, so you'ld have a lean mass around 58 kg, 33 kg of fat, 36% BF, which would make you look clearly obese.